What a Mammogram Could Do for You: Study Lays Out Risk & Benefits

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To maximize the benefits and lower the risks of routine
mammograms for breast cancer screening, it's best to base
decisions on each woman's individual risk level, as well as her
values and priorities, researchers concluded after reviewing 50
years of studies on mammograms.

Recommendations about who should get
mammograms and how often remain controversial.
Mammography is performed routinely with the goal of catching
breast cancer early, but it is unclear if early diagnosis is
necessary or even effective in reducing deaths from breast
cancer.

Moreover, regular screening may harm women by leading to
unnecessary treatment of benign tumors that would not have caused
medical problems if left untreated.

In the review study, published today (April 1) in the journal
JAMA, researchers attempted to tease out the overall benefits and
harms of mammograms, as well as what each woman stands to gain or
lose from undergoing routine mammograms. [ 9 Risk Factors for Breast
Cancer ]

"What I tell my patients is that the mammogram is not a perfect
test," said study researcher Dr. Nancy Keating, an associate
professor of health care policy at Harvard Medical School and
associate professor of medicine at Brigham and Women's Hospital.
"Some cancers will be missed. Some people will die of breast
cancer regardless of whether they have a mammogram, and a small
number of people that might have died of breast cancer without
screening will have their lives saved."

Based on their results, the researchers estimated that among
every 10,000 women in their 40s who undergo yearly mammography
for 10 years, about 190 will be diagnosed with breast cancer. Of
those 190, the researchers estimated that about 5 will avoid
death from breast cancer due to the screening test. Meanwhile,
about 25 of the 190 would die of breast cancer regardless of
whether or not they had mammograms. The rest will survive, thanks
largely to advances in breast cancer treatment.

The researchers also estimated that about 36 of the 190 women who
received annual mammography for 10 years and were diagnosed with
breast cancer would receive unneeded surgery,
chemotherapy or radiotherapy.

Among women in their 40 and 50s who undergo 10 years of annual
mammograms, 61 percent will get at least one
false positive mammogram, which would entail additional
scans and unnecessary biopsies.

In 2009, the
U.S. Preventive Services Task Force reversed its
previous recommendation of mammography every one to two years
beginning at age 40, and recommended routine screening every two
years starting at age 50.

However, recent data suggests that use of mammography in the
United States has not changed following the updated
recommendations, the researchers said.

The new study also showed that older women gained more from
mammography than their younger counterparts. The reduction in
mortality was about 15 percent for women in their 40s, and 32
percent for women in their 60s.

In general, breast cancer risk rises with age, and women in their
50s and 60s likely receive more benefit relative to their risk of
being harmed by a mammogram, the researchers said. For women ages
40 to 49 who get regular mammograms for 10 years, 5 of 10,000
will be saved because of mammograms. For women ages 50 to 59
years, 10 of 10,000 will be saved, and for women ages 60 to 69
years, 42 of 10,000 will be saved, according to the study.

Keating noted that factors other than age come into play when
deciding whether to undergo routine mammograms. Women who have
limited life expectancy due to a medical problem are also highly
prone to get
harmed by overdiagnosis, as older women are, she said.

Other factors, including family history, whether and when a woman
has given birth, and
lifestyle, also change how much a woman's risk of breast
cancer, and how much she might gain or lose by getting
mammograms.

"While we need more research on mammography's benefits and harms
today, existing data suggest that we have been overestimating the
benefits of mammography and underestimating the harms over the
years," said Dr. Lydia Pace, study co-author and research fellow
in women's health at Brigham and Women's.

"It is really important to have informed discussions with our
patients to help them understand the chances that a mammogram
will benefit them as well as the possible downsides of getting a
mammogram, so that they can incorporate their own values and
preferences in making the right decision for themselves."